PHP输出数组具有相同的标识符

I will need to output an array something along the lines of

 [
 0 => ['text' => 'category'],
 1 => ['text' => category']
 ]

So basicly an array for each category in my database. I need to output them like this because of how they will be exported to another site. (I cannot foreach inside the export)

My current code, is a foreach loop that runs through my categories. If i var_dump my field variable inside the foreach loop i get the result i want, but as mentioned i need to export everything in the format like above out of the foreach loop.

Code:

foreach ($categories as $category) {
            $fieldvalue = ['text' => $category->categoryname];

        }

What i have tried:

• Putting the array in a string to explode outside the loop-
• Result: Because of the "same identifier" issue i could only export the last result

What i need to be done:

My current code outputs the array as a text string so basicly

$fieldvalue ? "['text' => '$category->categoryname']";

And my output will be

array:4 [
  0 => "['text' => value1]"
  1 => "['text' => value2]"
  2 => "['text' => value3]"
  3 => "['text' => value4]"
]

I just need to get the string to be an array.